Problem: Simplify the following expression: $k = \dfrac{8}{4r + 5} \div \dfrac{5}{6r}$
Solution: Dividing by an expression is the same as multiplying by its inverse. $k = \dfrac{8}{4r + 5} \times \dfrac{6r}{5}$ When multiplying fractions, we multiply the numerators and the denominators. $k = \dfrac{ 8 \times 6r } { (4r + 5) \times 5}$ $k = \dfrac{48r}{20r + 25}$